Re: [PATCH v2 3/5] arm64: dts: allwinner: a523: Add EMAC0 ethernet MAC

Andre Przywara
2025-04-25T09:41:35Z

On Fri, 25 Apr 2025 13:26:25 +0800
Chen-Yu Tsai <wens@csie.org> wrote:

Hi Chen-Yu,

> On Thu, Apr 24, 2025 at 6:09 PM Yixun Lan <dlan@gentoo.org> wrote:
> >
> > Add EMAC0 ethernet MAC support which found on A523 variant SoCs,
> > including the A527/T527 chips. MAC0 is compatible to the A64 chip which
> > requires an external PHY. This patch only add RGMII pins for now.
> >
> > Signed-off-by: Yixun Lan <dlan@gentoo.org>
> > ---
> > arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi | 40 ++++++++++++++++++++++++++
> > 1 file changed, 40 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi b/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > index ee485899ba0af69f32727a53de20051a2e31be1d..c9a9b9dd479af05ba22fe9d783e32f6d61a74ef7 100644
> > --- a/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > +++ b/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > @@ -126,6 +126,15 @@ pio: pinctrl@2000000 {
> > interrupt-controller;
> > #interrupt-cells = <3>;
> >
> > + rgmii0_pins: rgmii0-pins {
> > + pins = "PH0", "PH1", "PH2", "PH3", "PH4",
> > + "PH5", "PH6", "PH7", "PH9", "PH10",
> > + "PH14", "PH15", "PH16", "PH17", "PH18";
> > + allwinner,pinmux = <5>;
> > + function = "emac0";
> > + drive-strength = <40>;
>
> We should probably add
>
> bias-disable;
>
> to explicitly turn off pull-up and pull-down.

Should we? I don't see this anywhere else for sunxi, probably because it is
the (reset) default (0b00).
I wonder if we have a hidden assumption about this? As in: if no bias is
specified, we assume bias-disable? Then we should maybe enforce this is in
the driver?

Cheers,
Andre